I do it a bit different, I house 2 females in one tub, and leave them together full time. yes there can be some baby hording by one of the females but it hasn't been a problem for me. I have also caught them trading babies back and forth. I cycle a male through each tub for a week, then move him on to the next tub I have enough racks that this gives the females at least a month if not more between litters. and that is from the time the pups are removed until they are bred again. If a female doesn't breed on the third try she is put in the feeder bin, same if there is a noticable drop in litter size.
Now I have been considering switching to only having one female per tub, but that is because 2 full litters from two healthy females can easily overrun a standard size mortar tub before the babies are weaned, meaning I have to do a bunch of extra cleaning to keep the odor under control.